CONDITION
Achilles Tendon Injury
The common calcaneal tendon — often called the Achilles tendon — is a structure formed from several muscle tendons in the back of the hind leg that attach to the calcaneus, the bone at the point of the hock. When this tendon is torn, ruptured, or strained, the hock tends to drop toward the ground and the leg loses much of its normal push-off strength. Owners often notice a sudden change in how the leg is carried, sometimes after a known injury but sometimes with no clear cause. Injury to this tendon can occur through a wound that cuts it, through sudden overstretching during activity, or through gradual weakening over time. The way it presents varies with the type and extent of damage — a partial strain may cause only mild lameness and some thickening, while a complete rupture often produces a distinctive flat-footed stance. This page explores what an owner may observe at home, what is happening within the tendon and surrounding structures, how the injury is investigated through examination and imaging, and the range of approaches that exist — from rest and immobilisation through to surgical repair — each with its own profile of recovery and outcome.
Why this matters now
Injuries to the common calcaneal tendon can occur at any age, though the pattern varies. In younger dogs — particularly those under two years — forceful activity may cause an avulsion fracture where the tendon pulls away from the calcaneus. In middle-aged and older animals, particularly larger breeds such as Doberman Pinschers and Labrador Retrievers, gradual weakening of the tendon over time can lead to partial or complete rupture, sometimes with no obvious inciting event. Cats tend to experience these injuries across a wide age range, often through trauma or in some cases without a clear external cause.
The way the injury evolves depends on the type and extent of damage. A sudden complete rupture may appear within minutes, with an immediate change in how the leg is held and used. Partial injuries or those developing through chronic degeneration may begin with subtle stiffness or mild lameness that worsens over days to weeks, particularly after exercise. In some cases the tendon fibres continue to fail progressively, and what begins as a partial strain may become a complete rupture if the remaining intact fibres give way.
Signals & patterns
Early signals
Mild hind-leg lameness after activity
The dog or cat may appear slightly stiff or reluctant to put full weight on the affected leg following exercise or play. This can be subtle and may improve with rest, only to return when the animal is active again.
Swelling behind the hock
The area along the back of the lower hind leg, just above the point of the hock, may appear thicker or feel warm to the touch. This thickening can be firm or soft and may develop gradually over several days.
Slight dropping of the hock
When standing or walking, the hock may sit a little lower than on the opposite leg, though the animal can still bear weight. This change in posture may be more noticeable when the animal is tired or after it has been lying down.
Reduced willingness to jump or climb
An animal that usually jumps onto furniture or climbs stairs may begin to hesitate or refuse, particularly when the movement requires pushing off with the affected hind leg. The change in behaviour may be gradual and easy to attribute to other causes.
Later signals
Flat-footed or plantigrade stance
The hock drops markedly toward the ground, and the animal walks with the back of the hock and sometimes the foot flat on the floor, rather than standing on the toes. This stance is often most obvious when weight is placed on the leg.
Visible gap or depression in the tendon
In cases of complete rupture, a distinct gap or soft, sunken area may be felt or seen along the back of the leg where the tendon has separated. The muscle above may also appear bunched or contracted higher up the limb.
Inability to extend the hock normally
The leg loses its usual spring and push-off strength. When the animal tries to walk or stand, the hock may flex excessively or fail to straighten properly, and the gait becomes inefficient and awkward.
Click to read about the biological mechanisms
How this is usually investigated
Investigation typically begins with a detailed history of when the lameness started, whether there was any known injury, and how the leg has been used since. Observation of the animal standing and walking often reveals the characteristic dropped-hock posture or altered gait. From there, palpation of the tendon and imaging are used to confirm the diagnosis and determine the extent and location of damage.
Physical examination
Radiography
Tendon ultrasound
Magnetic resonance imaging (MRI)
Options & trade-offs
Management of common calcaneal tendon injury varies with the type, location, and completeness of the tear, as well as the individual animal's size, activity level, and overall health. Approaches range from controlled rest and external support through to surgical reconstruction, and most plans combine elements of immobilisation, rehabilitation, and monitoring. What proves workable for one owner and animal may differ from what suits another, and the choice often reflects practical considerations as much as the injury itself.
Immobilisation with external coaptation
The leg is placed in a cast or splint that holds the hock in extension, reducing tension on the tendon and allowing the torn fibres to approximate and heal. The cast is typically worn for six to eight weeks, with periodic changes to monitor the skin and adjust fit as swelling resolves. This approach is most often considered for partial tears or in cases where surgical repair is not pursued.
Trade-offs: External support can allow healing without surgery, but the tendon that reforms tends to be longer and less mechanically efficient than the original, which may result in a permanent lowering of the hock and reduced push-off strength. Casts carry a risk of pressure sores, muscle atrophy, and joint stiffness, and compliance can be difficult in active or anxious animals.
Surgical repair
The torn tendon ends are identified and sutured together, often using specialised tendon-suture techniques and sometimes augmented with grafts or synthetic material to reinforce the repair. Post-operative immobilisation with a cast or splint is usually required for several weeks to protect the repair while early healing occurs. Surgery is most often pursued for complete ruptures, particularly in younger or more active animals.
Trade-offs: Surgical repair offers the potential for a shorter, stronger tendon and better functional outcome, but it requires general anaesthesia, carries the risks of infection and wound complications, and does not guarantee a return to pre-injury function. Rehabilitation is prolonged, and re-rupture can occur if the repair is loaded too early or if the tendon tissue was significantly degenerate before injury.
Controlled activity and rehabilitation
Following either conservative or surgical management, a structured programme of gradual exercise reintroduction, passive range-of-motion exercises, and sometimes hydrotherapy or physiotherapy is used to rebuild strength, maintain joint mobility, and encourage controlled loading of the healing tendon. The intensity and duration of activity are increased incrementally over weeks to months, guided by the animal's response.
Trade-offs: Rehabilitation can improve functional outcome and reduce the risk of stiffness or muscle loss, but it requires time, owner commitment, and sometimes access to specialised facilities. Progress varies between individuals, and overly rapid advancement can lead to re-injury or stretching of the healing tissue.
Pain management
Non-steroidal anti-inflammatory drugs or other analgesics may be used in the early stages to manage discomfort associated with inflammation and tissue injury. Pain control can make the animal more comfortable during immobilisation and may facilitate early rehabilitation exercises once the acute phase has passed.
Trade-offs: Effective pain relief can improve quality of life and compliance with restricted activity, but it does not address the underlying tendon damage. Over-reliance on pain medication without appropriate rest or immobilisation may mask worsening injury, and some animals experience gastrointestinal or renal side effects with prolonged use.
Common misconceptions
"If the leg is still bearing some weight, the tendon cannot be completely torn."
Animals with a complete rupture of the common calcaneal tendon often continue to place the foot on the ground and may even walk on it, though the hock drops lower and the gait is altered. The other tendons and ligaments around the hock can provide some support, allowing partial weight-bearing even when the main tendon is fully severed.
"Tendon injuries heal quickly because the area is well supplied with blood."
Tendons have a relatively poor blood supply compared to muscle, and healing is slow. The repair tissue that forms is initially weak and disorganised, and remodelling can take many weeks to months. Premature return to normal activity can result in re-injury or elongation of the healing tendon.
"Surgery always restores full function and the leg will be as strong as it was before the injury."
Surgical repair can improve outcomes, particularly in terms of hock angle and push-off strength, but most animals experience some degree of permanent change. The repaired tendon may remain slightly longer or less elastic than the original, and some reduction in athletic performance or endurance is common, particularly in working or sporting dogs.
Related conditions
Achilles Mechanism Rupture
Achilles mechanism rupture encompasses injuries to the tendon and associated structures described on this page, along with breakdowns elsewhere in the system of tissues that connect the calf muscles to the point of the hock. The two terms describe overlapping territory, and some sources use them interchangeably.
Cruciate Ligament Disease in Dogs
Dogs with chronic hind-limb lameness from cruciate ligament disease may alter their gait in ways that place unusual stress on the Achilles tendon, and both conditions share patterns of weight-bearing difficulty and changed movement that owners may observe in similar ways.
Carpal Hyperextension Injury
Carpal hyperextension and Achilles tendon injury both involve damage to the ligaments or tendons that stabilise major weight-bearing joints in the limbs, and both can produce a characteristic dropped or sinking appearance at the affected joint when the animal attempts to bear weight.
Bicipital Tenosynovitis
Bicipital tenosynovitis affects a tendon in the front limb in a manner that shares features with Achilles tendon injury—inflammation, pain on movement, and sometimes thickening of the tendon or its sheath—though the location and specific mechanics differ between shoulder and hock.
Understanding the anatomy and typical time course of tendon healing can help in recognising what changes are expected during recovery and what might warrant a conversation with the veterinary team. The interplay between rest, immobilisation, and controlled activity is central to most management plans, and observing how the leg is used over time provides useful information. For animals with underlying conditions such as hypothyroidism or hyperadrenocorticism, exploring how these may have contributed to tendon degeneration is sometimes a useful avenue.
Last reviewed: 13 September 2026 · Dr Alastair Greenway MRCVS